Conservation of heat energy in heating, drying, and other industrial processes



p 7, 1955 w. w. SPOONER CONSERVATION OF HEAT ENERGY IN HEATING, DRYING AND OTHER INDUSTRIAL PROCESSES Filed Aug. 21, 1950 10w P4555 v46 1/4751? 6764M Hana M91 00? 414 2 g IE T pump 5 DRY/Al? B I ,f, K/HTEK a 57-59 Hall I arm/M Inventor United States Patent (f) CONSERVATION OF HEAT ENERGY IN HEATING, DRYING, AND OTHER INDUSTRIAL PROCESSES William Wyclilfe Spooner, llkley, England Application August 21, 1950, Serial No. 180,678 Claims priority, application Great Britain August 25, 1949 4 Claims. (Cl. 3435) The present invention relates to the conservation of heat energy in heating, drying and other industrial processes.

The present invention consists in pumping a vapour, such as steam, mechanically by means, for example, of a pump or ejector to raise its pressure and thus enhance its availability.

The invention is especially applicable to low pressure steam which might not otherwise be usable to any material extent for industrial processes, and in many applications of the invention it will be possible to avoid loss of latent heat of steam or other vapour by mechanically increasing its pressure.

In many cases low pressure steam might be available but might not be readily re-usable in accordance with the present invention because it may, for example, be mixed with air. In such cases, according to the present invention, the steam or the mixture of steam and air, which may be at low temperature and pressure, may be used for raising low pressure steam whose pressure may then be increased mechanically, as by a pump or ejector. Thus, a further feature of the present invention consists in raising steam at low pressure by heat interchange with a source of low temperature heat such as waste heat, and then mechanically increasing the pressure of the steam so raised.

A still further feature of the invention consists in raising steam at a pressure less than atmospheric by heat interchange with a source of low temperature heat such as waste heat, and using a pump or ejector or other mechanical means to maintain the low pressure of the steam being generated and to increase its pressure after it has been generated.

When steam or other vapour is raised at low pressure by low temperature waste heat, the heating medium is preferably passed round a closed circuit and repeatedly caused to flow at relatively high speed over the surfaces containing the material to be heated, so that interchange of heat can be achieved with relatively small temperature differences between the heating and heated media.

Thus, for example, a suitable form of heat interchanger may consist of a set of gilled heating coils or tubes in which the steam is raised, the said heating coils or tubes being arranged in a closed circuit with a fan, and the heating medium passed in closed circuit from the fan to the heating coils and from the heating coils back to the fan. Whereas in conventional heat interchangers the rate of fiow of the heating medium through the system is usually about equal to the rate of inflow of the heating medium into the system, the rate of flow of the heating medium through the system in the case of my heat interchanger is much greater than and preferably a multiple of the rate of inflow of the heating medium. For example, the rate of flow of the heating medium through the fan and thus past the heating coils may be between ten and twenty times the rate of inflow of the heating medium.

The invention is very applicable, for example, to the conservation of heat energy in paper-making machines,

where relatively large quantities of steam at atmospheric pressure and containing air are given olf (as from an M. G. cylinder). Such steam may be passed through a heat interchanger as described above to raise steam at a pressure less than atmospheric, such steam being drawn by a pump to maintain the pressure within the heat inter changer at a value less than atmospheric and then to increase its pressure on discharge from the pump. Thus, for example, steam in the heat interchanger may be raised at a pressure of 5 lbs. less than the atmosphere and may be discharged from the pump at 10 lbs. per sq. inch above atmosphere. The steam discharged by the pump may be fed back to the M. G. cylinder to heat the same, and the condensate from the M. G. cylinder may be returned to the heat interchanger and again converted into steam, whereby loss of both latent and sensible heat is, to a material extent, avoided.

The invention is not however applicable solely to vapours at low pressure.

Thus, in an industrial process where steam or other vapour is used so as to reduce its pressure from a higher pressure to a lower pressure, one feature of the present invention consists in mechanically increasing the pressure of the steam after it has been used to enable it to be reused for the same or a different purpose, or to enable it to be re-used more efiiciently for the same or a different purpose.

Again, in an industrial process where steam or other vapour at one pressure is produced by the consumption of steam or other vapour at a higher pressure, a further feature of the invention consists in increasing the pressure' of said produced steam or other vapour mechanically to enable it to be used for the purpose for which said consumed steam was used or for some other purpose.

The invention is further described with reference to the accompanying drawings in which the figure is a diagrammatic illustration of how the invention can be ap: plied to a drying roll of a paper-making machine.

The figure illustrates diagrammatically a drying roll 1 of a paper-making machine having a hood 2 thereabove to entrap the mixture of vapour and air which is given off as a result of drying. The drying roll 1 is steam heated and the steam is initially supplied to the roll through valve 3 and pipe line 4. The mixture of vapour and warm air entrapped in the hood 2 is drawn by a fan 5 into a heat interchanger casing 6 through which passes a coiled tube 7 to which water is fed at the end 8. The fan 5 causes the mixture of vapour and air to flow at high velocity in closed circuit as illustrated by the arrows 9, 10 and 11 with a volume rate of flow which is high as compared with the rate of inflow of the mixture from the hood 2 and preferably a multiple thereof. By virtue of the rapid re-circulation of the air-vapour mixture in the heat interchanger casing 6 it is possible to raise steam in the coil 7 at a temperature not greatly less than the temperature of the circulating mixture. The outlet end 12 of the tube 7 is connected to a compressor 13 which discharges through a valve 14 to the pipe line 4 so that when the valve 14 is open and the valve 3 is closed or partially closed the compressor will deliver steam to the drum 1.

It will be appreciated that the compressor serves to facilitate the generation of steam by the maintenance of a low pressure in the tube 7. This pressure is preferably less than atmospheric, for example pressure may be 5 lbs. per sq. inch below atmosphere, and the compressor may raise the pressure of the steam thus generated to pressure of say 5 lbs. per sq. inch above atmosphere.

If desired the condensate from the drum 1 may be fed to the tube 7 whereby to avoid loss of the sensible heat of the condensate. Likewise condensate from the casing 6 maybe drawn, ofhfirornt-hedrain 15 and fed to the tube 7.

I. laim;

1. In a paper making process wherein paper in the course of production is passed over drying rolls heated y: s eam an results; in: he. product-ion; of a. mixtu e of water; vapor and; air. outside he; dry ng rolls, he 5126121015 thd awing a d mixture, into; a, closed Qha-mben having a hea xc a ging; me ns passing thcreth-rou h, the step of circulating said; mixt-upqwithin, said: chamber. about said, means at: a, velocity in; excess ofthe velocity at; whichsaid mixture; enters said; chamber, the StQP1Of generating steam. within said; means by reducing the pressure therein to a pointat; which the; temperature of said; circulating mixe u e ll; anor ze; Water; within; s id means to form. steam, he t p Q i withdr w ng s id; steam, from said; means, at-. sai fid lfidz Pressure and; subsequently increasing: the pressu of; said, steam, and; the; step. of using said steam: t; ncr ased pr ssure o achi ve further dryi 2, In a; paper; making process; according-toclaim. 1, thestep; of generating the said. steam at; a, pressure less; thanthat of the atmosphere and the step. of using, mechanical means such, as; apnmp to: maintain, thev low pressure of the steam being generated and to increase its.- pressure fter: it h e n. gener ted;

3:. In a paper rnaking rnachine including aisteamiheated drying; roll; having; a hood enclosing at. least an. upperportion; thereof to collect at least some of a mixture of water vapour and air'producedas-a result of drying, the

provision of a heat interchanger including means.- to re ceive, a mixture of water; vapour and; air from. said: hood, at least one steam generating passage in said heat: interchangenmeans to feed Water, into, said steam generating Passagev and means to permit the withdrawal of steam therefrom, means tocirculate said mixture insaid heat interchanger in a closed circuit in heat interchange rela- 'tiOIlShiP-With saidsteam generating passage, and a pump connected at itsinlet side to said steam generating passage to enable said pump to draw steam at low pressure from said steam generating passage andjto deliver it at increased pressure to achieve further drying,

4. In a paper making machine including a steam heated drx nsrq lhav na ahccd enclos ngatle st he ppc Portion thereof to collect at least some of a mixture of Water vapour and air produced as a result of drying, the provision of a heat interchanger casing, at least one steam generating tube contained in said casing, an inlet in said casing to receive at least some of said mixture of water vapour and air from said hood, a, drain connection to said.

casing to, permit removal of condensed water vapour out of said mixture, a water inlet connection to said steam generating t e, a. steam, outlet connection, from said steam generating tube, a fan adapted to draw a mixture of water vapour and air from said hood andto circulate it in closed circuit through said casing. and. to cause it toimpinge at high velocity on said steam generating tube with a volume rate of flow greater than and preferably a multiple of the rate at which said mixture is drawn off from said hood and a pump connected at its inlet side to the steam outlet ofrsaidi steam generating tube to enable said pump. to. draw. steam at; low pressure from said steam generating tube and to deliver it at increased pressure to achieve: further: drying.

References Cited in the file of this patent UNITED STATES. PATENTS 585,943- Waterhouse July 6, 1 897 808,649- Forbes Jan. 2,1906 838,195 LeSueur A Dec. 11, 1906 1,150,713. Soder-lund Aug. 17, 1915 1,501,513 Bobcrg Y July 15; 1924 1,602,545 Murphy Oct. 12, 1926 1,966,938, Stone July 17, 1934 1,995,999 Oman o Mar. 26, 1935 2,192,163 Bell Mar. 5, 1940 2,284,165 Porwauchen May 26, 1942 2,492,754.- Martin; Dec. 27, 1949 2,574,298 Smith t v tv Nov; 6, 1951 FOREIGN PATENTS.

643,,87-1- Germany Apr.,19, 1937 

